There are several circumstances that require the recording of phone conversations. These circumstances typically address one of three purposes: lawful intercept, personal note taking, and non-repudiation of contracts.
Providing non-repudiation of verbal agreements and recording of conversations that might result in a financial transaction to avoid issues of insider dealing has been mandated by government regulation in several countries. The financial industry particularly has this requirement. Lawful intercept has different considerations, and will typically be carried out by authorities (police or security services) in the relevant jurisdiction. These authorities will typically have some form of privileged access to a network, rendering the technical considerations involved in lawful intercept somewhat different from those involved in recording of conversations by a private party such as a bank (even if this voice recording is required to meet a legal obligation).
While calls to and from fixed office phones can be intercepted and recorded using local switch or private branch exchange (PBX) features, the position is much more complicated when a relevant subject (hereafter termed “subscriber”) uses a mobile phone, call recording is much more involved.
The mobile recording problem is partially addressed by providing a two stage dialing service. The mobile subscriber originates calls into an appropriate service (this may be a feature in their office PBX, for example). This service prompts for a second number to be called using a send call leg. The voice call (or other “media” in the call) from both call legs passes through the PBX and is recorded. Calls terminated to the mobile subscriber must return via the same path. Typically, the mobile terminated calls are made via some form of automated call forwarding or diversion, but a two-stage dialer such as used for the mobile originations may also be used.
There are several problems with this two stage dialing approach. Firstly, it requires the subscriber to behave in a different way compared to their behaviour in a conventional call. Secondly, if the subscriber wishes to have a call that is not recorded, they can simply bypass this procedure by dialling directly. Thirdly, a caller can simply call the mobile's number directly, again bypassing the recording service (unless the mobile number is disabled for incoming calls at least.)
To address these objections in part at least, mobile terminals, particularly “smart phones,” have been programmed to automate the two-stage dialing and to intercept the normal call progression. However, such applications are easily bypassed, disabled, or the equipment changed. Moreover, direct mobile call termination is not addressed. Additional problems occur. The call set up path and the onward path to the B party require independent signalling processes. It is often the case that timing mismatches occur between the two signalling paths and this can cause either long call setup times or frequent failed call set ups.
Lawful intercept solutions may involve making a copy of media that is split between a recording device and the destination using in-region recorders are used. This is not desirable for a commercial application, where it is desired to use one home recording service for all recording regardless of where the person has traveled to in the world. Lawful intercept is also different in that it does not provision a services to subscribers or employers of subscribers—it operates under specific restraints (it typically must not interfere with the call if it cannot be recorded) and it will not involve provision of an announcement made to either caller.
A better solution to these concerns can be made by using features of the intelligent network associated with the relevant telecommunications backbone—these may be used to give a service controller the opportunity to redirect the call path to the call recorder. On a GSM network, for example, the set of triggers, detection points, and associated architecture that can be used is referred to as “CAMEL” (“Customised Applications for Mobile Networks Enhanced Logic”, defined by a set of standards specified in ETSI TS 123 078). The subscriber cannot bypass this type of automated feature as it resided within the network and is a part of that network. The subscriber handset, often labelled ‘User Equipment’ (UE) in these standards, is unaware of the process going on.
Within a country or region, such a network-controlled divert to a call recorder can perform well. Over great distances, particularly intercontinental distances, a call path which routes back to the home office and then out again to another part of the world may have objectionable media delay resulting in an unacceptable call experience. If we were to record a call in the London office of a user while they were travelling in Australia the audio delay on the call could be over 1 second. Toll quality voice really needs less than 250 ms maximum and ideally 150 ms or less to allow people to engage in normal dialogue with the natural interruptions that this entails.
It is desirable to address the problems of the prior art to find an effective solution to the recording of voice calls.